config: differentiate scope from project scope in config

Fixes: npm/npm#14412
PR-URL: npm/npm#14477
Credit: @zkat
Reviewed-By: @iarna

lib/cache/caching-client.js

@@ -215,6 +215,6 @@ function adaptConfig (config) {
     defaultTag: config.get('tag'),
     couchToken: config.get('_token'),
     maxSockets: config.get('maxsockets'),
-    scope: config.get('scope')
+    scope: npm.projectScope
   }
 }

lib/npm.js

@@ -300,12 +300,9 @@
         var lp = Object.getOwnPropertyDescriptor(config, 'localPrefix')
         Object.defineProperty(npm, 'localPrefix', lp)
 
-        if (config.get('scope') === '') {
-          config.set('scope', getProjectScope(npm.prefix))
-        }
-        if (config.get('scope') !== '' && config.get('scope')[0] !== '@') {
-          config.set('scope', '@' + config.get('scope'))
-        }
+        config.set('scope', scopeifyScope(config.get('scope')))
+        npm.projectScope = config.get('scope') ||
+         scopeifyScope(getProjectScope(npm.prefix))
 
         // at this point the configs are all set.
         // go ahead and spin up the registry client.
@@ -411,6 +408,10 @@
     require('../bin/npm-cli.js')
   }
 
+  function scopeifyScope (scope) {
+    return (!scope || scope[0] === '@') ? scope : ('@' + scope)
+  }
+
   function getProjectScope (prefix) {
     try {
       var pkg = JSON.parse(fs.readFileSync(path.join(prefix, 'package.json')))